/pdf/processes-of-carbonate-precipitation-in-modern-microbial-176vfhaypi.pdf

Processes of carbonate precipitation in modern microbial mats

Microbiological deterioration and degradation of synthetic polymeric materials: recent research advances

A field experiment was conducted in Delaware (USA) to evaluate three crude oil bioremediation techniques. Four treatments were studied: no oil control, oil alone, oil + nutrients, and oil + nutrients + an indigenous inoculum. The microbial populations were monitored by standard MPN techniques, PLFA profile analysis, and 16S rDNA DGGE analysis for species definition. Viable MPN estimates showed high but steadily declining microbial numbers and no significant differences among treatments during the 14-weeks. Regarding the PLFA results, the communities shifted over the 14-week period from being composed primarily of eukaryotes to Gram-negative bacteria. The Gram-negative communities shifted from the exponential to the stationary phase of growth after week 0. All Gram-negative communities showed evidence of environmental stress. The 16S rDNA DGGE profile of all plots revealed eight prominent bands at time zero. The untreated control plots revealed a simple, dynamic dominant population structure throughout the experiment. The original banding pattern disappeared rapidly in all oiled plots, indicating that the dominant species diversity changed and increased substantially over 14 weeks. The nature of this change was altered by nutrient-addition and the addition of the indigenous inoculum.

/pdf/microbial-population-changes-during-bioremediation-of-an-46czbde8f8.pdf

Microbial Population Changes During Bioremediation of an Experimental Oil Spill

Polyhydroxyalkanoates, biopolyesters from renewable resources: Physiological and engineering aspects

Thematic Review Series: Sphingolipids. Biodiversity of sphingoid bases (“sphingosines”) and related amino alcohols

http://diposit.ub.edu/dspace/bitstream/2445/155222/1/585210.pdf

Denitrification of groundwater with pyrite and Thiobacillus denitrificans

Enhanced denitrification in groundwater and sediments from a nitrate-contaminated aquifer after addition of pyrite

Physiological status of microbial mats of the Ebro Delta (Tarragona, Spain) based on the extraction of lipids considered ``signature lipid biomarkers'' (SLB) from the cell membranes and walls of microorganisms has been analyzed. Data from a day–night cycle show significant differences in viable cells countings (PLFA cells counts) ranging from 1.5 × 1010 to 5.0 × 1010 cells g−1 of sediment. Minimum values were observed at 18:00 and 6:00, when physicochemical conditions change drastically. The diversity of the microbial community was assessed by GC/MS analysis of phospholipid fatty acids (PLFA). The ratio of PLFA, representative of Gram-negative bacteria, comprises 47.8% of the total PLFA of the microbial mat community. The remaining PLFA was representative of Gram-positive (10.0%), anaerobic (5.7%), and eukaryotic microorganisms (5.7%), and other common lipids. Two different approaches were used as a comparative study to assess the physiological status of the microbial mats. Two parameters (cyclopropane fatty acids/ω7c monoenoic fatty acids, and measurement of the trans/cis monoenoic PLFA ratio) showed a minimum at midnight, suggesting the highest microbial activity. Higher values were observed at 18:00 and 6:00, coinciding with lower PLFA cell counts.

/pdf/physiological-status-and-community-composition-of-microbial-7qp10itjmf.pdf

Physiological Status and Community Composition of Microbial Mats of the Ebro Delta, Spain, by Signature Lipid Biomarkers

The effect of exposure of bacterial suspensions to UV radiation by means of the dose-response curves was assessed. The D37 and D10 values were used for subsequent statistical analysis of the results. The aim of this article is to evaluate the sensitivity to UV radiation of several microorganisms of different habitats (Rhizobium meliloti, Rhodobacter sphaeroides, Escherichia coli, and Deinococcus radiodurans), two mutants with nonfunctional SOS DNA repair system (R. meliloti recA- and E. coli recA-), and a mutant in the synthesis of carotenoids (R. sphaeroides crtD). The results reveal that D. radiodurans was an extremely resistant bacterium, R. meliloti was more resistant than R. sphaeroides, and E. coli was the most sensitive bacterium tested. The high sensitivity of recA- mutants was also verify. Moreover, it seems that the possession of pigments had no important effect in the sensitivity of R. sphaeroides to UV radiation.

Sensitivity of selected bacterial species to UV radiation

The distribution and types of microbial mats of the Ebro Delta (Catalonia, Spain) are described. The studied area is La Banya spit, formed by a narrow sand bar and a peninsula, located south of the main body of the Ebro Delta. Sea water can penetrate into the back shore through channel inlets, cutting the steeper coastal barrier of the open sea side of the spit or through the complex drainage channel system of the low-energy beaches in the inner Alfacs Bay. Sea water can stay in the back shore almost permanently, trapped in isolated depressions and lagoons. The surface distribution of microbial mats in La Banya spit has been studied by means of a detailed interpretation of vertical aerial photographs and field work consisting of mapping and sampling. The observed different ratios of cyanobacteria, as well as the presence and thickness of the layers of anoxygenic sulfur phototrophic bacteria, depend on the moisture content, the system stability, and the age of the microbial mat. Lyngbya, Oscillatoria , and Spirulina are the first cyanobacteria able to colonize the bare sediment. Lyngbya dominates in young microbial mats and in mats exposed to frequent desiccation. Microcoleus is the second most important colonist in the microbial succession. In relation to water, the alternation of emergence and submergence is optimal for the maximal development of Microcoleus -dominated microbial mats. We classify the microbial mats of the Ebro Delta into five main types: (i) Lyngbya -dominated type, in which the anoxygenic phototrophic bacteria are absent and the black layer of sulfate-reducers is very thin; (ii) Spirulina -dominated type; (iii) Oscillatoria -dominated type, which is found only at one site and covers a small area — this type, like the Spirulina -type mat, is not common in the Ebro Delta; (iv) Lyngbya/Microcoleus -transition type, in which Microcoleus and Lyngbya coexist in similar proportions — in the more developed mats of this group a layer of purple bacteria is usually present, and the black layer of sulfate-reducers is usually also well developed; and (v) Microcoleus -dominated type — in La Banya spit, this type is found in localities with relatively stable conditions. These areas are wet during most of the year. After appropriate conditions of diagenesis, the most highly developed microbial mats may be preserved as laminated hard sediments. The field study has been completed with cultivation, isolation, and identification of the main cyanobacterial genera under laboratory conditions.

Jordi Urmeneta

Papers

Denitrification of groundwater with pyrite and Thiobacillus denitrificans

Enhanced denitrification in groundwater and sediments from a nitrate-contaminated aquifer after addition of pyrite

Physiological Status and Community Composition of Microbial Mats of the Ebro Delta, Spain, by Signature Lipid Biomarkers

Sensitivity of selected bacterial species to UV radiation

Distribution of types of microbial mats at the Ebro Delta, Spain